using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
class Solution {

    static int minimumNumber(int n, string password) {
        // Return the minimum number of characters to make the password strong\
        int []a=new int[4];
        for(int i=0;i<n;i++)
        {
            if(password[i]>=65&&password[i]<=90)
                a[0]++;
             if(password[i]>=97&&password[i]<=122)
                a[1]++;
             if(password[i]>=48&&password[i]<=57)
                a[2]++;
            if(password[i]=='!'||password[i]=='@'||password[i]=='#'||password[i]=='$'||password[i]=='%'||password[i]=='^'||password[i]=='&'||password[i]=='*'||password[i]=='('||password[i]==')'||password[i]=='-'||password[i]=='+')
                a[3]++;
        }
        int c=0;
        for(int i=0;i<4;i++)
        {
            if(a[i]>0)
                c++;
        }
        c=4-c;
        int d=6-n;
        if(n<6)
        {
            if(d>c)
                return d;
            else
                return c;
        }
        else 
            return c;
            
            
            
    }

    static void Main(String[] args) {
        int n = Convert.ToInt32(Console.ReadLine());
        string password = Console.ReadLine();
        int answer = minimumNumber(n, password);
        Console.WriteLine(answer);
    }
}